Electrical control for a dishwasher



Nov. 21, 1961 5, ox ETAL 3,009,466

ELECTRICAL CONTROL FOR A DISHWASHER Filed Jan. 2, 1959 FIG- 33 (5 so 34 32 4s 1 ,6 115 Z PM A 11/ 47 za so f I \(L 1 I k I I 75 1a 22 I4 12, 54 55/2, 80

FIG-2 7a a /4 /5 6( J\ i "1H U so INVENTORS GERALD B. FOX a BY STANLEY O. THOMAS nite state tent 3,069,466 ELECTRICAL CQNTRQL FOR A DISHWASHER Gerald lit. Fox and Stanley 0. Thomas, Troy Ohio, assignors to The Hobart Manufacturing Company, Troy, Ohio, a corporation of Ohio Filed Ian. 2, 1959, Ser. No. 784,508 8 (llaims. (Cl. 134-58) This application relates to dishwashing apparatus, particularly to controls for dishwashing machines of the conveyor type which carry the articles to be washed through stations having washing and rinsing apparatus.

In such dishwashing machines, which are relatively large and or" relatively high capacity, once the machine is started and the conveyor is in operation, the dishes are stacked on the conveyor at the loading end by an operator and pass through one or more washing units where washing liquid is sprayed over the dishes (and through the open grid conveyor structure) and thence past a final rinse station to the unloading station where the dishes are removed from the conveyor by another operator. If the unloading operator cannot, for one reason or another, keep up with the machine, passage of dishes past the unloading station will be sensed by a safety device which will stop the conveyor. However, if there are no dishes in the conveyor it is possible for the machine to continue running with the operators away from their respective stations, power is wasted in driving the conveyor, and there is considerable waste of hot fresh final rinse Water supplied to the final rinse spray mechanism. Obviously, if the machine is permitted to run empty in such a way for any considerable period of time the waste of fresh Water and power will be considerable.

Accordingly, the primary object of this invention is to provide in conveyor type dishwashing machines a control circuit which senses the presence of an operator, particularly at the unloading station, and which will stop the conveyor and the fiow of rinse liquid in the event that the operator is absent from his station.

Another object of this invention is to provide such a machine with a control which will sense either the absence of an operator from the unloading station or the passage of dishes or other Washed articles past the unloading station, and in either event will stop the conveyor and the rinse liquid spray.

Another object of this invention is to provide such a control circuit in which the presence of an operator at other stations, for example at the loading station, may also be sensed, such that absence of any operator will result in shut off of the conveyor and the flow of axial rinse liquid, and wherein one operator may run the washing machine temporarily if the other operator is absent.

Other objects and advantages of this invention will be apparent from the following description, the accompartying drawings and the appended claims.

In the drawings:

FIG. 1 is a schematic side View, with parts broken away to show interior details, of the type of automatic dishwasher with which the present invention is particularly concerned;

FIG. 2 is a somewhat schematic top plan view of FIG. 1 showing the location of the switch control mat at the unloading operators station; a

FIG. 3 is a wiring diagram of a control circuit applied to the dishwashing machine;

FIG. 4 is a plan view of a modified form of the inven tion, showing the location of additional switch mats at other control operators stations; and

FIG. 5 is a partial wiring diagram corresponding to the modified arrangement shown in FIG. 4.

Referring to the drawings, which illustrate a preferred embodiment of the present invention, FIG. 1 shows an automatic dishwasher having a base 10 supported on a plurality of legs 12 and in turn supporting a housing 14 and a hood 15 covering the central part of the housing between the entrance or loading end 16 and the exit or unloading end 18. The space beneath hood 15 is divided to provide a scrapping chamber 2h including a tank 22 and a pump 23 for recirculating water from the tank to a plurality of upper spray nozzles 25 and a lower spray manifold 26, to spray water over the dishes as they pass through chamber 2% and wash oif particles of food. These particles fall into tank 22 and are collected at a removable filter (not shown) from which they are subsequently removed for disposal. A curtain 28 covers the entrance to chamber 20 to reduce splashing of water out of the machine.

Adjacent the scrapping chamber is a washing chamber 30 and a rinsing chamber 32, separated from each other by a deflector 33 and a flexible curtain 34. A tank 35 extends beneath washing chamber 319, and liquid from tank 35 is delivered by a pump (not shown) to upper and lower revolving washing arms 36 and 37, respectively, for spraying the washing liquid over the dishes as they are conveyed through the washing chamber. Similarly, a tank 40 extends beneath rinsing chamber 32, and liquid from this tank is recirculated by a power rinse pump (not shown) through revolving upper and lower power rinse arms 42 and 43. In addition, final rinse manifolds 45 and 46 are provided adjacent the eXit of rinsing compartment 32, just within the exit deflector curtain 47, and are connected to a hot water supply line 43 which provides a source of hot water under pressure for giving the cleansed dishes a final rinse of clear hot water.

The water supply to the scrapping section is provided partially from detergent overflow water from wash tank 35, passing into tank 22 through a connecting pipe 49, and partially from a connecting pipe 49 to the final rinse supply. Part of the fresh final rinse water is thus diverted to tank 22 as make-up water, and the spray from the final rinse manifolds drains into tank 40 as make-up water in the power rinse section.

A shaft 50 carrying a pair of sprockets 52 is journaled transversely of the unloading end of the machine, and is driven by a motor 53 and speed reducer unit 54 suitably connected to shaft 50, as shown schematically at 55. A similar shaft 56 is supported across the loading end of the machine and sprockets 58 are rotatably sup ported thereon, with the conveyor es extending around the sprockets for driving through the hood 15 with the upper flight thereof passing from the loading to the unloading ends of the machine. It will be understood that the above describes a suitable type of machine in which the present invention may be advantageously used.

Thus, the loading operators station, indicated generally at is adjacent the head or loading end of the machine where he can place dishes or other articles to be Washed on conveyor 60. The unloading station at the other end of the machine, indicated generally at 78, is defined by a switch met or platform of the type commonly used for controlling opening of doors by the presence of sufiicient weight on the mat to close a switch in a control circuit. This switch mat is included in a control circuit which is arranged to permit operation of the conveyor drive and supply of fresh final rinse water to the manifolds 45 and 46 only when an operator is standing on mat 80, and thus in position to unload the conveyor. There is also a safety switch control incorporated in the hood S2 at the unloading end of the machine Which is capable of sensing the presence of dishes in the conveyor at a point past the unloading station. De-

3 tails of this safety switch mechanism are shown in the patent to Fox et al. 2,644,473, issued July 7, 1953 to the assignee of this application, particularly in FIGS. 11 and 12 of that patent.

The circuit in which the mat switch control 80 is included preferably is a low voltage control circuit, to eliminate danger around the machine where the floors and surrounding areas may be wet. Thus, referring to FIG. 3, the primary winding of a transformer 85 is connected across the electrical supply indicated by lines L1 and L2, and the secondary or low voltage winding is connected in series with the mat control switch 80 and the coil of a relay R1 having a single set of normally open contacts CR1. Thus, whenever an operator is standing at the unloading station relay R1 is engaged and contacts CR1 are closed.

The contacts CR1 are connected in series with switch 87 which is normally closed, and is adapted to be open by the safety switch mechanism in the hood 82 as dishes pass beyond the unloading station. Also in this series circuit are two normally closed push-button stop switches 90 and 92, which may be located at separate control boxes at opposite ends of the machine for manipulation by the operators. First and second start switches 93 and 94 are wired in parallel with each other, and this parallel is connected in series with the aforementioned elements to provide for closing of the circuit when either of the start switches, which are normally opened, are closed by the operator. These switches also may be located in separate control boxes, along with the first and second stop switches, at separate stations on the machine.

Another parallel circuit in this line includes a relay R2 and solenoid valve 95, the latter being connected in the fresh hot water final rinse supply 48 to control flow therethrough. Relay R2 has two sets of contacts, the first set 1CR2 being connected in shunt across start switches 93 and 94 to provide a lock-in circuit after starting, and the second set of contacts 2CR2 being connected across the power supply in series with the conveyor drive motor 53. A thermal overload element 98 also is included in this circuit and controls normally closed contacts 99 in the supply lines to the control relay R2 such that if there is an overload in the motor supply line contacts 99 will be opened to deenergize relay R2, opening the motor circuit and the holding circuit through contacts 1CR2.

In operation, assuming that an operator is standing on the mat 80, and relay R1 is energized, if either of the start switches is momentarily closed by an operator relay RZ will be energized and solenoid valve 95 will be opened. This closes the contacts 1CR2 to lock-in the energizing circuit for these two elements and also closes contacts 2CR2, resulting in starting of conveyor drive motor 53. If at any time the operator leaves the unloading station and steps off the mat switch 80, relay R1 is deenergized, opening contacts CR1 which in turn deenergizes the solenoid valve 95 and the coil of relay R2, stopping the flow of final rinse water and also stopping conveyor drive motor 53.

In FIG. 4 additional switch mats 100, 101 and 102 are shown in the loading station and on opposite sides of the unloading end of the machine, providing alternate unloading stations. Obviously, suitable control circuits can be provided along the above described lines incorporating these switch mats in any number of different arrangements to assure that the operators are in proper position before the conveyor drive is started and the flow of final rinse water is commenced. For example, the portion of a suitable circuit for controlling relay R1 from the switch mats 100, 101 and 102 is shown in FIG. 5. The remainder of the circuit would be the same as shown in FIG. 3. With this circuit the conveyor and final rinse sprays would function so long as operators were stationed at the loading station and at the unloading station and at either of the switch mats 101 or 102.

Of course, with the control mats at both ends of the machine it is necessary to have both loading and unloading operators present to run the machine, and in some instances this might be a disadvantage, for example when it is necessary to have one operator run the machine temporarily. Therefore, a conventional biased-open switch is connected in shunt across switch mat 100, and may be controlled by a knee operated lever or the like (not shown) adjacent one of the stations provided by the mats 101 and 102. Of course, any suitable arrangement can be provided whereby switch 105 is operated from levers at either of the stations provided by mats 101 and 102. Thus, an operator at the discharge station may run the machine alone provided he stands on the mat and presses a lever or the like with his knee to close switch 105. Such an arrangement will leave the operators hands free to unload dishes from the machine.

Also, in order to permit the single operator to load the machine and start it into operation, a further biasedopen knee operated switch 107 is connected in parallel with the parallel wired mats 101 and 102-. The lever or other mechanism (not shown) for switch 107 is located at the loading station in a position where the operator may stand on mat 100 and close switch 107 by movement of his knee or the like, thus enabling a single operator to advance the conveyor and operate the machine so long as he remains at the loading position and deliberately closes switch 107.

Accordingly, the present invention provides control systems which automatically assist in running dishwashers of the type disclosed herein with the best possible economy. After dishes are cleared from the machine and the staff of operators leaves for any reason, as during a lull in the operating time, the conveyor and the flow of final rinse water is automatically stopped. This conserves the fresh final rinse water, which may flow in a machine of this type at rates up to approximately 7 g.p.rn. and at a temperature of about F., and also conserves the power used otherwise to drive the conveyor.

While the forms of apparatus herein described constitnte preferred embodiments of the invention, it is to be understood that this invention is not limited to these precise forms of apparatus and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a dishwashing machine of the character described a housing having a loading station at one end thereof and an unloading station at the other end, a conveyor extending between said stations, means for driving said conveyor in a direction to move toward said unloading station, means intermediate said stations for spraying a washing liquid over articles to be cleansed carried by said conveyor, a spray head between said washing means and said unloading station adapted to spray rinse liquid over the articles, a supply source of rinsing liquid and a valve between said supply source and said spray head for controlling the flow of rinse liquid to said spray head, means defining an unloading position for an operator including switch operating means upon which the operator must stand during operation of the machine, a switching circuit including said switch operating means, and a control circuit including said valve and said conveyor drive means connected to said switching circuit for energization of said drive means and opening of said valve only in response to operation thereof indicating continuing presence of an operator.

2. In a dishwashing machine of the character described a housing having a loading station at one end thereof and an unloading station at the other end, a conveyor extending between said stations, means for driving said conveyor in a direction to move toward said unloading station, means intermediate said stations for spraying a washing fluid over articles to be cleansed carried by said conveyor, a spray head between said washing means and said unloading station adapted to spray rinse liquid over the articles, a supply source of rinsing liquid and a valve between said supply source and said spray head for controlling the flow of rinse liquid to said spray head, means defining an unloading position for an operator including switch operating means upon which the operator stands during operation of the machine, switching circuit means operative in response to presence of an operator on said switch operating means, and a control circuit including said valve and said conveyor drive means connected to said switching circuit means for energization of said drive means and opening of said valve in response to operation thereof indicating presence of an operator, a second switch operating means at said unloading station operative in response to movement of articles on said conveyor past said unloading station, and a connection between said second switch operating means and said control circuit providing for stopping of said conveyor and closing of said valve in response to operation thereof.

3. In a dishwashing machine of the character described a housing having a loading station at one end thereof and an unloading station at the other end, a conveyor extending between said stations, means for driving said conveyor in a direction to move articles toward said unloading station, means intermediate said stations for spraying a washing liquid over articles to be cleansed carried by said conveyor, a spray head between said washing means and said unloading station adapted to spray rinse liquid over the articles, a supply source of rinsing liquid and a valve between said supply source and said spray head for controlling the flow of rinse liquid to said spray head, means defining a loading position for an operator including first switch operating means upon which the operator stands during operation of the machine, signal means operative in response to presence of an operator on said switch operating means, means defining an unloading position for another operator including second switch operating means upon which the operator stands adjacent said unloading station during running of the machine, signal means operative in response to presence of an operator on said second switch operating means, and a control circuit including said valve and said conveyor drive means and both said switch operating means connected to energize said drive means and open said valve only in response to operation of both of said signal means indicating presence of operators at said loading and unloading stations.

4. A washing machine of the character described comprising means deiining a loading station and means defining an unloading station, a conveyor extending between said stations, drive means for said conveyor connected to move said conveyor from said loading to said unloading stations, means intermediate said stations for spraying washing liquid through said conveyor to cleanse articles carrier thereon, a spray head between said washing means and said unloading station adapted to spray rinsing liquid over the articles, means for supplying rinsing liquid to said spray head including a control valve, normally open switch means at said unloading station adapted to be closed in response to continued presence of an operator at said unloading station to remove cleansed articles from said conveyor, and a control circuit including said switch means connected to said valve and to said conveyor drive means for stopping said conveyor and cutting off the flow of rinse liquid in response to opening of said switch means.

5. A washing machine of the character described comprising means defining a loading station and means defining an unloading station, a continuous conveyor extending between said stations, means connected to drive said conveyor to move the upper flight thereof from said loading to said unloading stations, means intermediate said stations for spraying washing liquid through said conveyor to cleanse articles carried thereon, a spray head between said Washing means and said unloading station adapted to spray rinsing liquid over the articles, means for sup plying rinsing liquid to said spray head including a control valve arranged to control the flow of rinse liquid, first normally open switch means at said unloading station adapted to be closed in response to continued presence of an operator at said unloading station to remove cleansed articles from said conveyor, second normally open switch means at said loading station adapted to be closed in response to continued presence of an operator at said loading station to place articles to be cleansed on said conveyor, and a control circuit including both said switch means in series connected to said valve and to said conveyor drive means for stopping said conveyor and cutting off the flow of rinse liquid in response to opening of either of said switch means.

6. A washing machine of the character described comprising means defining a loading station and means defining an unloading station, a continuous conveyor extending between said stations, means connected to drive said conveyor to move the upper flight thereof from said loading to said unloading stations, mean-s intermediate said stations for spraying washing liquid through said conveyor to cleanse articles carried thereon, a spray head between said washing means and said unloading station adapted to spray rinsing liquid over the articles, means for supplying rinsing liquid to said spray head including a control valve arranged to control the flow of rinse liquid, first normally open switch means at said unloading station adapted to be closed in response to presence of an operator at said unloading station to remove cleansed articles from said conveyor, second normally open switch means at said loading station adapted to be closed in response to presence of an operator at said loading station to place articles to be cleansed on said conveyor, a control circuit including both said switch means in series connected to said valve and to said conveyor drive means for stopping said conveyor and cutting off the fiow of rinse liquid in response to opening of either of said switch means, and switch means operable from said loading station connected to bypass said first normally open switch means providing for deliberate operation of said machine by a single operator at said loading station.

7. A washing machine of the character described comprising means defining a loading station and means defining an unloading station, a continuous conveyor extending between said stations, means connected to drive said conveyor to move the upper flight thereof from said loading to said unloading stat-ions, means intermediate said stations for spraying washing liquid through said conveyor to cleanse articles carried thereon, a spray head between said washing means and said unloading station adapted to spray rinsing liquid over the articles, means for supplying rinsing liquid to said spray head including a control valve arranged to control the fiow of rinse liquid, first normally open switch means at said unloading station adapted to be closed in response to presence of an operator at said unloading station to remove cleansed articles from said conveyor, second normally open switch means at said loading station adapted to be closed in response to.pre sence of an operator at said loading station to place articles to be cleansed on said conveyor, a control circuit including both said switch means in series connected to said valve and to said conveyor drive means for stopping said conveyor and cutting oil the flow of rinse liquid in response to opening of either of said switch means, switch means operable from said loading station connected to bypass said first normally open switch means providing for deliberate operation of said machine by a single operator at said loading station, and bypassing switch means operable from said unloading station and connected to shunt said second normally open switch means providing for deliberate operation of said machine by a single operator stationed at said unloading station.

8. A washing machine of the character described comprising means defining a loading station and means defin- 7 ing an unloading station, a continuous conveyor extending between said stations, means connected to drive said conveyor to move the upper flight thereof from said loading to said unloading stations, means intermediate said stations for spraying washing liquid through said conveyor to cleanse anticles carried thereon, a spray device between said washing means and said unloading station adapted to spray rinsing liquid over the articles, means for supplying rinsing liquid to said spray head including a control valve arranged to control the flow of rinse liquid, first normally open switch means at said loading station adapted to be closed in response to continued presence of an operator at said loading station to place articles to be cleansed on said conveyor, second normally closed switch means mounted on said machine in position to sense articles carried by said conveyor beyond said unloading station, and a control circuit including both said switch means in series connected to said valve and to said conveyor drive means for stopping said conveyor and terminating the flow of rinse liquid in response to opening of either of said switch means.

References Cited in the file of this patent UNITED STATES PATENTS 2,114,537 Lewis Apr. 19, 1938 2,201,380 Tierney May 21, 1940 2,611,836 Crawford Sept. 23, 1952 2,644,473 Fox et al July 7, 1953 2,764,170 Messler et a1 Sept. 25, 1956 2,830,311 Vizdos Apr. 15, 1958 2,903,854 Harty Sept. 15, 1959 2,929,893 Ferry et al Mar. 22, 1960 FOREIGN PATENTS 949,840 Germany Sept. 27, 1956 

